There are kits made for that sold at home depot. Step by step instructions are in the kit. Prep is very important.
If you don't want to paint, you could cover with Tile sticky backed covers, or Stencil on them or use transfers...........
stencil still requires paint. Kelli is correct. Get the correct paint and make sure ALL OF THE SOAP RESIDUE IS SCRUBBED off or the paint will not stick.
There are many ways to do so. Here are some of them.